Which method is usually used to treat plants with most of their leaf area above the water surface?

The method typically used to treat plants with most of their leaf area above the water surface is spray application. This technique is effective for applications because it allows for direct contact with the foliage, ensuring that the treatment can adequately cover the leaves where absorption takes place. When plants are largely above the water, using a spray allows the active ingredients to penetrate the leaf surface effectively and reach the target areas of the plant.

In contrast, other methods like drip application are suited for targeted applications to the soil rather than the leaf surface, while granular application is generally more effective for soil treatment rather than direct foliar treatment. Subsurface injection is specifically utilized for treatments below the water surface and would not engage the leaf area exposed above the water effectively. Therefore, spray application is the most appropriate choice for managing treatment in this scenario.